alginate impressions

Ttoday we did alginate impressions on pts. some were edentulous, some were dentate. Note that there are two different trays for these but dentate trays can be used in edentulous patients with large ridges.

Lower impressions: May ideally be taken first as it is easier for the pt to tolerate i.e. doesn't tend to go down their throat and so it can give them a chance to feel the impression and expect what happens next and puts a bit of trust in you (provided you don't screw up). Things you'd like to capture for F/F dentures are:
- The retromolar pad (whole length)
- Ridges to their entirety
- depth of the sulci: Labial and lingual
- Frenal areas (Buccal, lingal and labial)
- External oblique ridge

Have the pt seated with their mouth just higher than relaxed elbow level so you don't have to stretch down as their jaw will open and depress further

Upper impressions: More difficult to tolerate for the pt but it is important to keep them calm and tell them to breathe through their nose and distract them with things like (wiggle your toes). You want to capture:
- mx tuberosities
- mx ridge in its entirety
- Buccal and labial sulcus
- hard palate at least up to the vibrating line
- palatine rugae
- incisive papilla
- buccal and labial frena

Have the pt seated for the upper impession with their mouth at relaxed elbow level

Feel for Md or palatine Tori or read the pts oral exam notes. You should take these into account as undercuts when making your impression. If you take a bad impression, retake it because it will carry errors all the way down the line to your completed project and you will waste a lot of time and money trying to fix your error.

When checking your impression you want to look out for things like:
- air bubbles
- Distortions
- all the relevant anatomy is captured
- no tears
- ideally shouldn't see any part of the tray

how to take the impression:
1. Try the tray in the pts mouth. Extend with periphery wax if necessary
2. have a DA mix the alginate: 3 scoopsfor upper as you have to capture the additional palate area and 2 scoops for lower with the equivalent cups of water. Mix in a flattening motion by flattening it along the bowl and periodically scraping it all into one mass. You have to be very fast.... Don't dilly dally.
3. use a paddle pop stick to scrape the alginate off the spatula onto the impression tray
4. Use a mirror to retract the pts corner of mouth laterally. Have them open wide and rotate the tray to contact THE OTHER corner of the mouth with the part of the tray that should rest there when the impression is taken. then rotate the tray the other way to enter the mouth. slide the mirror from the corner of the mouth to the middle of the lip to pull the lip forward
5. at this point you'll have the tray hovering above the teeth. Look into the mouth and see if everything's alright. push down on the tray to "enter" the teeth. always keep at least one finger on the tray to hold it against the teeth but DON'T lean on the tray which will cause distortions
6. when it is set, break the seal of the impression by pulling up and out the lip and snap removal of the tray. (quick and snappy)